Vacuum packaging method and apparatus

ABSTRACT

Vacuum packaging method and apparatus for heat sealable bags in which a clamp is used to effect a temporary air-tight seal of an evacuated bag while the bag is transported through a region of atmospheric pressure to a heat sealer. After heat sealing to effect a permanent air-tight closure, the clamp is open and the bag removed.

TECHNICAL FIELD

The present invention relates generally to a method and an apparatus forvacuum packaging food items in heat sealable plastic bags.

BACKGROUND OF THE INVENTION

Vacuum packaging in heat sealable plastic bags is a conventional way ofpackaging food items such as whole fowl, cuts of meat, cheese bricks andthe like for sale at retail. Vacuum packaging involves placing the fooditem in a heat sealable plastic bag and then communicating the bag to apartial vacuum to evacuate air from the bag and collapse it about thefood item. The bag is heat sealed in its evacuated condition so the fooditem becomes encased in a generally air-free environment.

It also is customary to fabricate the bag from a heat shrinkable plasticfilm. After sealing, the bagged food item is immersed in hot water orotherwise exposed to heat to shrink the bag so it is tight about thefood item. This makes the bag substantially wrinkle-free and enhancesthe appearance of the bagged article for retail sale.

Apparatus, as disclosed for example in U.S. Pat. No. 3,958,391, has beendeveloped to automate the vacuum packaging operation. The apparatus asdisclosed in this patent has a plurality of platens arranged formovement along a closed path of travel. Each platen includes a heatsealer and is adapted to receive a bagged article wherein the open mouthof the bag is draped across the heat sealer.

During the course of moving through its closed path of travel, eachplaten merges with a vacuum chamber. The chamber presses against theplaten and, for a portion of the path, it moves along with the platen.During this time the chambers are evacuated to remove air from the bagsand the heat sealers are operated to close the bags. Each vacuum chamberthen vents to atmosphere and thereafter separates from the platen so thebagged article can be removed.

Since each platen has its own heat sealer, provision must be made forsupplying electrical power to each platen moving along the path oftravel. It also is customary to supply each platen with other utilities.For example, water is supplied for cooling the heat sealer andpressurized air is supplied for closing the heat sealer. The need formultiple heat sealers and for supplying several utilities to each platencompounds maintenance problems and the systems required to supplymultiple utilities to each moving platen adds to the complexity of thesystem.

The present invention eliminates the need for multiple heat sealers andfor the delivery of electrical power, cooling water and other utilitiesto each platen moving through a closed path of travel. Instead, eachplaten in the present invention is provided with a mechanically operatedclamp. The clamp closes about the bag after evacuation and maintains thebag in an evacuated state even after the vacuum chamber separates fromthe platen. The path of travel followed by each platen carries it to aheat sealing zone containing at least one operable heat sealer whichoperates to heat seal each bag carried by a platen through the heatsealing zone.

SUMMARY OF THE INVENTION

A vacuum packaging method of the present invention can be characterizedby the steps of:

a) placing an open article-containing sealable bag at a loading zone anddrawing the open neck of the bag to a flat width over a first clampsurface;

b) moving the article-containing bag and first clamp surface in to anevacuation zone and at least partly evacuating air from the bag throughthe open neck while holding the neck at substantially its flat widthover the first clamp surface;

c) moving a second clamp surface against the first clamp surface in theevacuating zone and clamping the bag neck therebetween for effecting atemporary gas-tight seal of the evacuated, article-containing bag;

d) moving the evacuated, article-containing bag from the evacuation zonethrough a region of atmospheric pressure to a sealing zone andmaintaining said temporary gas-tight seal during said movement throughthe atmospheric pressure region;

e) sealing the clamped bag neck across its flat width in the sealingzone thereby effecting a permanent gas-tight seal closure of the bagneck; and

f) moving the permanently sealed, evacuated, article-containing bag fromthe sealing zone to an unloading zone, unclamping the bag neck andremoving the permanently sealed article-containing bag from between thesaid clamping surfaces.

A vacuum packaging apparatus of the present invention can becharacterized by:

a) a carrier adapted to receive an open-necked bag containing an articleto be packaged, said carrier being transportable through successiveloading, evacuating, sealing and unloading zones;

b) said apparatus having a region of atmospheric pressure between saidevacuating and sealing zones;

c) clamp means on said carrier movable between an open position and aclosed position and being constructed and arranged to clamp said openbag neck to substantially its flat width;

d) drive means on said carrier for moving said clamp means between saidopen and closed positions;

e) first activating means in said evacuating zone for activating saiddrive means to move said clamp means to said closed position after atleast partial evacuation of said article-containing bag to effect atemporary air-tight seal of said article containing bag and thereaftermaintaining said clamp means in said closed position during movement ofsaid carrier through said region of atmospheric pressure;

f) sealing means in said sealing zone for effecting a permanentair-tight seal closure of said clamped bag neck across its flat width;and

g) second activating means after said sealing zone for activating saiddrive means to move said clamp means to said open position therebyreleasing said bag neck and allowing the removal of said permanentlysealed article-containing bag from said carrier in said unloading zone.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a vacuum packaging apparatus inaccordance with an embodiment of the present invention;

FIG. 2 is a side elevation view partly broken away and in section takengenerally along lines 2--2 of FIG. 1 showing selected components of theapparatus of the present invention in a bag receiving position;

FIG. 3 is a plan view of FIG. 2 with portions broken away and insections to show selected components of the present invention;

FIGS. 4 and 5 are views similar to FIGS. 2 and 3 only showing selectedcomponents in a bag evacuating position; and

FIGS. 6 and 7 are views similar to FIGS. 2 and 3 only showing selectedcomponents in a bag clamping position.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 shows the apparatus of the presentinvention to comprise a plurality of bag receiving units each generallyindicated at 10. The units are spaced along a conveying means 12 formovement through a closed path of travel in the direction as indicatedby arrows 14. The conveying means preferably is an endless chain orconveyor belt.

Each bag receiving unit 10 has an elongated or generally rectangularconfiguration and includes a carriage 16 fixed to the conveying means12. The carriage is arranged such that its longer dimension is orientedparallel to the path of travel. Each bag receiving unit 10 also includesa platen 18 supported by the carriage. The platen is a carrier for thebag to be evacuated and heat sealed and it has a configuration similarto, but slightly smaller than, its associated carriage 16.

Each platen is journaled to its supporting carriage so that it can berotated to a position transverse the carriage path of travel. Thus, theplaten can pivot through an arc of about 90° from a first position,wherein it is substantially congruent with its supporting carriage, to asecond position wherein the platen is oriented so its longer dimensionextends transverse the supporting carriage.

The bag receiving unit path of travel 14 passes in sequence through aproduct load zone 20, an evacuating zone 22, a bag sealing zone 24, andan unloading zone 26. From the unloading zone the units return to theproduct load zone 20.

As the bag receiving units 10 enter the evacuating zone 22 they mergeand engage with evacuation chambers 28. The evacuation chambersgenerally are conventional and will not be described in detail. It issufficient for purposes of the present invention to say that thechambers are arranged on a carousel 29 so individual chambers merge withand engage against a corresponding bag receiving unit adjacent a pointof beginning 21 where the units 10 enter the evacuating zone 22. Thevacuum chambers remain merged and engaged with the bag receiving unitsas the units traverse the evacuation zone 22. At the end of theevacuation zone, the vacuum chambers 28 separate from the bag receivingunits 10. The units 10 shunt away from the vacuum chambers 28 as thecarousel 29 carries each vacuum chamber back to the point of beginning.

Various arrangements are available to provide for the merging andengagement of each vacuum chamber 28 with an associated bag receivingunit 10. For example, as shown in U.S. Pat. No. 3,958,391 the vacuumchambers are held in a horizontal plane while the bag receiving unitsare elevated until they engage against the bottom of the evacuatingchambers. An alternative and preferred arrangement as shown in U.S. Pat.No. 4,550,548 is to have the bag receiving units 10 remain in the samehorizontal plane and to lower the vacuum chambers until they meet andengage against the bag receiving units. For this purpose, eachevacuation chamber is supported on a radial arm 30 of the carousel.These arms 30 are hinged and are raised or lowered hydraulically by anysuitable means (not shown). A vacuum line (not shown) is provided forcommunicating each vacuum chamber to a vacuum pump (also not shown).

In the load zone 20, an operator takes a bagged food product 48 from aconveyor 49, lays it onto the platen 18 and pulls the bagged productuntil it contacts against an upstanding anvil 32. The operator arrangesthe open neck 56 of the bag to a flat width and drapes the bag neckacross the anvil 32. As the receiving unit leaves the loading zone, ittraverses a trip cam 34. As will be described hereinbelow, the trip camcauses a bag clamping mechanism (not shown) carried by the receivingunit to move to a first clamping position wherein it loosely holds theopen bag neck 56 to the anvil 32.

As the bag receiving units continue along the path of travel 14 theyindividually merge with one of the vacuum chambers 28 and enter theevacuation zone 22. In the evacuating zone the vacuum chambers 28 areevacuated and air is exhausted from the bags.

Prior to leaving the evacuation zone, the bag receiving units 10traverse a second trip cam 36. This causes the bag clamping mechanism tomove to a second position wherein it clamps the bag neck tightly againstthe anvil and closes it so that after the vacuum chamber vents andreleases from the platen, the bag resting on the platen is maintained inan evacuated state.

At the end of the evacuation zone 22, the vacuum chamber disengages andseparates from the bag receiving unit. After separation from the vacuumchamber, the platen 18 traverses a third cam 37. The engagement with cam37 causes the platen to rotate 90° with respect to its carriage 16 sothat the platen is positioned transverse the carriage path of travel. Inthis position the anvil 32 and the clamped bag neck 56 draped across theanvil are oriented parallel to the direction of the carriage path oftravel 14. The carriage continues along its path of travel and entersthe sealing zone 24 which contains a heat sealer 35. As the bagreceiving units 10 pass through the sealing zone, the heat sealereffects a heat seal closure of the bag neck draped across anvil 32.

As each bag receiving unit exits the sealing zone 24, the platens 18traverse a fourth cam 38 causing each platen to rotate 90° back to theposition where it is congruent with its carriage 16. The bag receivingunits 10 then enter the unloading zone 26 and traverse a fifth cam 39.This last cam causes the bag clamping mechanism to open so the bags, nowevacuated and heat sealed, can be removed from the platen 18 for furtherprocessing.

FIGS. 2 and 3 show a bag receiving unit in more detail. As shown in FIG.2, the carriage 16 has an upstanding hub 40 which pivotally supports theplaten 18. A detent mechanism 42 between the platen and carriage allowsthe platen to fix at either of the two positions noted above. That is,in one position the platen is in a congruent alignment with carriage 16and in a second position the platen is rotated 90° so it lies transversethe carriage. Any suitable detent mechanism may be provided and forpurposes of illustration, FIG. 2 shows the detent to include a ball 44which seats in either of two grooves 46 (only one of which is shown)defining the congruent and transverse positions.

The platen 18 defines the surface 45 for supporting a loaded bag 48 tobe heat sealed and the anvil 32 upstands from an end 50 of the platen.When the platen is congruent with carriage 16, the platen end 50 trailsin the direction of movement along the carriage path travel 14.

Anvil 32 has a substantially flat upper surface 52 which carries asealing member such as a gasket or O-ring 54. As shown in FIG. 2 theunsealed neck 56 of the bag 48 is draped across the anvil surface 52 andsealing member 54 such that a portion of the bag neck including the openbag mouth indicated at 58 extends across and overhangs the anvil. Asfurther described hereinbelow, the seal member 54 provides a firstclamping surface for effecting a mechanical air-tight closure of the bagmouth.

Platen 18 carries the components which are activated by the trip cams34, 36 and 39 for clamping and releasing the bag neck 56. Generally,these components as shown in FIGS. 2-7 are arranged in three cooperatingassemblies including a clamp assembly generally indicated at 60, a drivemeans generally indicated at 62 and an over center lock generallyindicated at 64.

The clamp assembly 60 includes the components which are movable to afirst position to loosely hold the bag neck to the anvil duringevacuation of the bag. These components also are movable to a secondposition to tightly close the bag neck after evacuation and maintain itclosed until heat sealing. The drive means 62 is suspended from beneaththe platen 18 by brackets, a portion of which is shown at 63. The drivemeans is operatively connected to the clamp assembly and it interactsdirectly with the trip cams 34, 39 respectively to close and open theclamp assembly. The over center lock 64 acting through the drive means62 acts to hold the clamp assembly at either an open or closed positionand applies a spring force to compliment the operation of the drivemeans.

Clamp Assembly

As shown in FIGS. 2 and 3, the clamp assembly 60 in the open position islocated away from and below anvil 32. This insures that the clampassembly does not interfer with loading the bagged product onto theplatten and draping the bag neck 56 over the anvil 32. The clampassembly 60 includes an elongated clamp bar 66 which is coextensive withanvil 32. The clamp bar is supported at its ends by clamp arms 68 onlyone of which is shown in the figures. The clamp arms 68 straddle theanvil and are pivotally connected to opposite sides of the platen. Onlyone clamp arm 68 is shown and the other is a duplicate pivotallyconnected to the opposite side of the platen. The arms are pivotable asfurther described hereinbelow to carry the clamp bar towards and awayfrom the anvil.

The clamp bar 66 has an elongated clamp member 74 which is engageableagainst seal member 54 as described herein below. Thus, the clamp member74 provides a second clamping surface which cooperates with the sealmember 54 for effecting a mechanical air-tight closure of the bag mouth.In addition, a portion of the clamp bar defines a channel 72 (FIG. 3)which is open in the direction towards the platen. Disposed within thechannel 72 is a pressing member 76 or "comb" having teeth 80 separatedby recesses 82. A spring 78 acts to bias the comb through the openchannel and against the anvil surface 52. The function of the comb 76 isto hold the bag neck loosely to the anvil surface and Yet still allowair to escape from the bag. In this respect, when the clamp bar is in afirst clamping position the teeth 80 provide lands which press portionsof the bag neck against the anvil surface 52 while the recesses 82between the teeth provide openings which allow air to excape from thebag.

The clamp bar 66 is moved towards and away from the anvil by thepivoting movement of clamp arms 68. As seen in FIG. 2, each clamp armhas an elongated slot 84. A fixed bearing 86 captured within the slotallows the clamp arm to pivot about the bearing and reciprocate withrespect to the bearing. This compound motion is necessary for the clampbar 66 to clear the bag open end 58 as it moves between the open andclosed positions. Each clamp arm 68 also has a projecting shoulder 88adapted to catch against a stop 90 which is slidably carried by theanvil 32. Catching the shoulder 88 against the stop prevents the clampbar 66 from closing tightly against the anvil during the evacuation ofair from the bag 48.

Drive Means

The drive means 62 is operatively connected to the clamp assembly by alink 92. The link is pivotally connected at one end 94 to the clamp arm68 and, at its other end, the link is fixed to a rotatable drive shaft96. Also fixed to the drive shaft is a pinion gear 98 which in turnmeshes with a spur gear 100. The spur gear is fixed to a shaft 102 andthe spur gear shaft 102 in turn is fixed at one end to a lever arm 104.As best seen in FIG. 3, the lever arm 104 is provided with a camfollower 106 that is tripped by the cams 34 and 39 (FIG. 1). In thisrespect, as the cam follower 106 traverses the first trip cam 34, thefollower is elevated. This moves the lever arm 104 clockwise as viewedin the figures and causes the shaft 102 and spur gear 100 to rotateclockwise. Pinion gear 98 is driven by the spur gear and rotates driveshaft 96 counter clockwise. The link 92, being fixed to the drive shaftlikewise is driven counter clockwise and this pivots and translates theclamp arm from the position shown in FIG. 2 to the first clampingposition shown in FIG. 4. Conversely, as the cam follower traverses tripcam 39, the follower is depressed. This triggers movement of the drivemeans in the opposite direction to return the clamp arm to the openposition shown in FIG. 2.

Over Center Lock

As discussed above, it is the operation of cam follower 106 whichtriggers the operation of the drive means. However, it is the overcenterlock assembly 64 which provides the force to facilitate the operation ofthe drive means and to stabilize the clamp assembly at either the openor closed positions.

The overcenter lock assembly is connected to the spur gear shaft 102 sothe force exerted by the over center lock assembly is transmitteddirectly to the drive means 62. In particular, FIG. 3 shows theovercenter lock includes a crank 108 connected eccentrically to spurgear shaft 102 by crank arm 110. A pair of tension springs 112 extendbetween the crank and the platen.

As shown in FIG. 2, the crank 108 is positioned below the axis of spurgear shaft 102. In this position the tension force of spring 112 isapplied below center and leverage is exerted for opening, and holdingopen, the clamp assembly.

As noted above, elevating the cam follower 106 drives the spur gearshaft 102 clockwise and this carries the crank 108 above the axis of thespur gear shaft. In this position, the tension force of spring 112 isapplied above center and leverage is exerted to close, and hold closed,the clamp assembly. It should be appreciated that the force exerted bysprings 112 is adjustable to control the closing force exerted by theclamp means. Such an adjustment can be accomplished by changing thespring constant of springs 112.

Operation

The operation will be described beginning with reference to FIGS. 2 and3. These figures show the position of components carried by the platen18 as each bag receiving unit 10 enters the loading zone 20.

In the loading zone, an open heat sealable bag containing an article tobe vacuum packaged is Placed onto platen 18 (FIG. 2). Preferably theproduct 51 within the bag is butted against the anvil 32 and the bag ispulled across the anvil so the length of bag material 53 between theproduct and the seal member 54 can be minimized thereby allowing the useof as short a bag as possible. Also, the bagged article 48 is arrangedso the neck 56 of the bag which drapes across the anvil surface 52 isstretched to its flat width so as to eliminate, as much as possible, anywrinkles in the portion of the bag disposed across the anvil.

The carriage 16 moves along its path of travel 14 and eventuallytraverses trip cam 34. The trip cam engages cam follower 106 anddeflects it upwardly which rotates spur gear shaft 102 clockwise asviewed in FIG. 2. The rotation of spur gear shaft 102 drives the meshedspur and pinion gears 100, 98 as described above and rotates link 92counter clockwise from the open position shown in FIG. 2 to the firstclamping position shown in FIG. 4.

As the link 92 rotates counter clockwise from its FIG. 2 position to itsFIG. 4 position it drives clamp arm 68 about the fixed bearing 86. Inthis respect, the engagement of the fixed bearing in the elongated slot84 causes the clamp arm 68 to translate with respect to the bearing asthe clamp arm pivots about the bearing. The result is that the clamp bar66 first is thrust above the level of anvil surface 52 and then is drawndownward toward the anvil surface. The clamp bar is drawn downwardlyuntil the shoulder element 88 on the clamp arm catches against the stop90 (FIG. 4).

The shoulder 88 catches against the stop 90 when the member 74 on theclamp bar 66 is still spaced above the anvil surface 52. However, sincethe comb 76 carried by the clamp bar is spring loaded, it is biasedoutwardly from channel 72 to the extent that its teeth 80 can pressportions of the bag neck 56 against the anvil surface 52.

The clockwise rotation of shaft 102 by the lever arm 104 (and camfollower 106) also pivots the crank arm 110 clockwise. This carries thecrank 108 from a position below the level of the spur gear shaft 102 asshown in FIG. 2 to the position shown in FIG. 4 wherein the crank isabove the level of the spur gear shaft. In this position, the forceexerted by springs 112 is transmitted by crank arm 110 and gears 98, 100and link 92 to the clamp arm 68. The clamp arms 68 are urged downwardlyby the spring force which firmly fixes shoulder 88 on the clamp armagainst the stop 90.

With the components in this position the bag receiving units 10 proceedalong the path of travel 14 (FIG. 1) to the point indicated at 21 wherethey merge with a vacuum chamber 28.

As noted hereinabove, the vacuum chambers carried by a carousel 29 aresupported at the end of radial arms 30. After merging with a bagreceiving unit, each radial arm lowers a vacuum chamber until thechamber seats against a carriage 16 and encloses the platen. The vacuumchamber and carriage then move into the evacuating zone 22 where thevacuum chamber 28 is communicated with a vacuum source to evacuate airfrom within the chamber and the bag. In the evacuation zone, FIG. 4shows that the lands provided by the teeth 80 of comb 76 hold portionsof the bag neck to the anvil surface 52. However, the unclamped spacesprovided by the recesses 82 (FIG. 3) between the lands allows air toescape from the bag.

Prior to leaving the evacuation zone, the vacuum chambers 28 are carriedpast the second trip cam 36. This triggers the operation of a plunger114 which, as shown in FIGS. 5, is carried by the vacuum chamber andextends slidably through the vacuum chamber wall 116 in alignment withstop 90. Seals 118 maintain an air tight seal between the plunger andthe chamber wall.

When the plunger is triggered by cam 36, it is pressed inward againstthe stop 90 and kicks the slide from under the clamp arm shoulder 88.

As shown in FIG. 6, this releases the clamp arm 68 so it immediately andforceably is drawn downwardly. In this respect, the tension of springs112 pulls the crank 108 farther over center and causes an additionalclockwise rotation of crank arm 110.

This additional rotation of crank arm 110 is transmitted through shaft102 and the meshed gears 100, 98 of the drive means 62 to link 92. Theresult is that the clamp arm 68 is drawn downwardly until the clampmember 74 on the clamp bar 66 is in its second sealing position seatedtightly against the seal member 54 on the anvil surface 52 and exerts apredetermined clamping force against the seal member. As the clamp bardraws down towards the anvil surface 52, the spring biased comb 76recedes into the channel 72 (FIG. 3) and does not interfer with theseating of the clamp member 74 against the seal member 54.

In this fashion there is provided a mechanical air-tight seal of the bagneck 56 draped across the anvil surface 52. The seal is effected with apredetermined clamping force which is sufficient to prevent air entryinto the bag.

The vacuum chamber is vented to atmosphere in a conventional manner andthe radial arms 30 are raised to separate the vacuum chamber from thecarriage. The venting of the chamber to atmosphere and the resultingrapid increase in the air pressure exerted against the exterior surfaceof the bag collapses the bag against the food article within the bag.Any air remaining in the bag is compressed by the collapsing bag. Thepressure of the compressed air exerts a force which exceeds thepredetermined clamping force of the clamp member 74 against the sealmember 54. The result is that any air remaining in the bag is forcedbetween the seal 54 and clamp member 74 and is expelled from the bag.

FIG. 1 shows that each vacuum chamber 28, now separated from itsassociated bag receiving unit 10, is carried around by the carousel 29to the point of beginning 21 until the bag receiving units shunt awayfrom the vacuum chamber along the path of travel 14. After the bagreceiving units leave the evacuation zone 22, a cam 37 disposed in thepath of travel of platen 18 engages the platen and rotates it 90° withrespect to carriage 16 so the longitudinal axis of the platen isoriented transverse the carriage path of travel 14. At the 90° position,detent 42 engages to hold the platen 18 from pivoting farther withrespect to the carriage 16. The platen, in this position, is carriedalong by the carriage into the sealing zone 24 where the portion of thebag neck 56 extending from the anvil 32 is heat sealed. During thecourse of its passage from the evacuating zone to the sealing zone, thebagged product 48 is exposed to atmospheric pressure. However the clampbar 66 remains in position to effect an air-tight mechanical seal of thebag neck 56.

By rotating the platen 90°, the portion of the bag neck draped acrossthe anvil 32 and extending out from under the clamp bar 66 is broughtinto alignment with a heat sealer 35. Preferably the heat sealer in thesealing zone is a band sealer. Band sealers per se are conventional andneed not be described in detail except to say that heat sealing isperformed by a pair of heated endless belts which press against layersof film moving between the belts. Accordingly, as the bag receivingunits move towards the band sealer, the neck portion of the bag neck 56draped across the anvil and extending from under the clamp bar 66 isguided between the endless belts of the band sealer. The belts heat andpress against the bag film to provide the bag neck with a permanent airtight heat seal without stopping the movement of the bag.

As the bag receiving units leave the sealing zone 24, cam 38 rotates theplaten 90° back to its carriage congruent position. The bag receivingunits continue along the path of travel and pass over cam 39. Cam 39engages the cam follower of the drive means 62 (FIG. 2) and deflects thecam follower counter clockwise as viewed in the figures. This causes thespur gear shaft 102 to rotate counter clockwise and reverses theoperation of the drive means 62. Reversing the operation of the drivemeans causes the clamp arms 68 to move vertically and then to rotate tothe open position as shown in FIG. 2. As the spur gear shaft 102 rotatescounter clockwise, it also carries crank 108 to a position below thespur gear shaft 102 (FIG. 2). In this position, the tension exerted bysprings 112 now holds the clamp bar 66 in the open position.

In this fashion clamp bar 66 is removed from the anvil surface 52 torelease the heat-sealed bag neck. The sealed bag is then removed fromthe platen either manually or by a mechanical pusher (not shown) and thebag receiving units return to the load zone where an operator placesanother open bag on the platen.

It should be appreciated that the vacuum packaging method and apparatusof the present invention provides a simplified arrangement for thecontinuous packaging of food items in heat sealable plastic bags.Multiple heat sealers, that is a heat sealer associated with each bagcarrying unit 10, are eliminated. The multiple heat sealers are replacedwith a mechanically operated clamping device which closes the bag afterevacuation and maintains it closed while the bags are sealed outside ofthe vacuum chambers. This arrangement allows a longer evacuation timebecause the time otherwise taken to effect a heat seal within the vacuumchamber can now be added to the evacuation time. Also, by effecting theheat seal outside the vacuum chamber the heat sealing cycle and the timefor cooling the heat seal can be increased. That is, the time taken forthese actions is not dictated by the time allowed for retention of thebags in the vacuum chambers. The method and apparatus of the presentinvention further simplifies machine design by eliminating the supply ofutilities such as electrical power, cooling water and compressed air toeach of the bag carrying units.

While one embodiment of the present invention has been described, otherarrangements within the scope of the appended claim are possible. Forexample, the sealing zone may contain two band sealers. In this way onewill provide back-up during maintenance or repair of the first. Also,the band sealer can be replaced by any other suitable heat sealingdevice such as an impulse sealer, an ultrasonic welder or a sealingdevice using radio frequency (R. F. sealer). If a sealer such as animpulse sealer is used, the movement of the platen must be halted duringheat sealing or the impulse sealer must be arranged to track themovement of the platen during heat sealing.

In still another arrangement a heat sealer in the sealing zone can bedisposed transverse the carriage path of travel 14 to avoid the need torotate the platen with respect to the carrier. If the heat sealer isdisposed transverse the carriage path of travel, it can be arranged todrop into position for engaging and sealing the portion of the bag neckextending from between the anvil and the clamp bar. In this case themovement of the carriages can be intermittent and in timed relation tothe operation of the heat sealer. As an alternative, the heat sealer canbe arranged to drop into position and then to track the movement of thecarriage through the sealing zone.

Having described the invention in detail, what is claimed as new is: 1.A method of vacuum packaging articles in sealable bags comprising thesteps of:a) placing an open article-containing sealable bag at a loadingzone and drawing the open neck of the bag to a flat width over a firstclamp surface; b) moving the article-containing bag and first clampsurface into an evacuation zone and at least partly evacuating air fromthe bag through the open neck while holding the neck at substantiallyits flat width over the first clamp surface; c) moving a second clampsurface against the first clamp surface in the evacuating zone andclamping the bag neck therebetween for effecting a temporary gas-tightseal of the evacuated, article-containing bag; d) moving the evacuated,article-containing bag from the evacuation zone through a region ofatmospheric pressure to a sealing zone and maintaining said temporarygas-tight seal during said movement through the atmospheric pressureregion; e) sealing the clamped bag neck across its flat width in thesealing zone to effect a permanent gas-tight seal closure of the bagneck; and f) moving the permanently sealed, evacuated,article-containing bag from the sealing zone to an unloading zone,unclamping the bag neck and removing the permanently sealedarticle-containing bag from between the said clamping surfaces.
 2. Amethod of vacuum packaging articles in sealable bags comprising thesteps of:a) providing a platen movable in a closed path throughsuccessive loading, evacuating and sealing zones; b) placing an opensealable bag containing the article to be package on the platen at theloading zone, drawing the open neck of the bag to a flat width anddraping it over a first clamp surface; c) moving the platen with thearticle-containing bag to an evacuation zone and at least partiallyevacuating air from the bag through the open neck; d) while maintainingthe partial vacuum, clamping the bag neck at its flat width to the clampsurface and thereby effecting a temporary air-tight seal of the bag; e)moving the platen from the evacuation zone to the sealing zone andexposing the bag in transit to atmosphere pressure while maintaining thetemporary air tight seal thereof; f) sealing the clamped bag neck acrossits flat width in the sealing zone to effect a permanent air-tight sealclosure of the bag mouth; and g) moving the platen from the sealing zoneto an unloading zone, unclamping the bag neck and removing the sealedbag.
 3. A method as in claim 2 wherein draping the bag neck over saidclamp surface orients the bag neck transverse the platen path of travel.4. A method as in claim 3 including rotating the platen with respect toits path of travel for orienting the bag neck in the direction of thepath of travel prior to entering the sealing zone.
 5. A method as inclaim 4 including continuously moving the platen through the sealingzone and sealing the bag neck during the transit thereof through thesealing zone.
 6. A method as in claim 5 including sealing the bag byprogressively and continuously forming a heat seal band across the bagas the bag traverses the sealing zone.
 7. A method as in claim 5including rotating the platen after sealing the bag neck back to aposition wherein the bag neck is oriented transverse the platen path oftravel.
 8. A method as in claim 4 including stopping the platen in thesealing zone and then effecting a permanent air-tight seal closure byheat sealing the bag.
 9. A method as in claim 2 wherein exposing theevacuated bag to atmosphere pressure at said moving step (e) collapsesthe bag against the food product therein and causes the expressing ofresidual air from said evacuated bag through said clamped bag neck. 10.A method as in claim 2 including adjusting the force applied forclamping the bag neck at step (d) to a predetermined value sufficient topermit the expressing of residual air from said evacuated bag throughsaid clamped bag neck upon the exposure of the evacuated bag toatmospheric pressure at said moving step (e).
 11. A method as in claim 1or 2 wherein clamping said bag neck is accomplished by moving a clampbar to a position pressing against the first clamp surface andmaintaining the clamp bar pressing against the first clamp surface withan overcenter applied spring force.
 12. A method as in claim 11 whereinunclamping is accomplished by pivoting the clamp bar against the springforce to an open position and maintaining the clamp bar in an openposition with an over center applied spring force.
 13. A method as inclaims 1 or 2 comprising holding the bag neck to the first clamp surfaceat a plurality of spaced locations and evacuating air from the bagthrough openings intermediate the spaced locations and thereafterclamping the bag neck to the first clamp surface for effecting saidtemporary air-tight seal.
 14. A method as in claim 2 including:a)providing the clamp surface on a support upstanding from the platen; andb) placing the open article-containing bag on the platen with the foodarticle in the bag located against the support thereby minimizing thelength of the bag neck extending between the food article and thetemporary air-tight seal.
 15. Vacuum packaging apparatus comprising:a) acarrier adapted to receive an open-necked bag containing an article tobe packaged, said carrier being transportable through successiveloading, evacuating, sealing and unloading zones; b) said apparatushaving a region of atmospheric pressure between said evacuating andsealing zones; c) clamp means on said carrier movable between an openposition and a closed position and being constructed and arranged toclamp said open bag neck to substantially its flat width; d) drive meanson said carrier for moving said clamp means between said open and closedpositions; e) first activating means in said evacuating zone foractivating said drive means to move said clamp means to said closedposition after at least partial evacuation of said article-containingbag to effect a temporary air-tight seal of said article containing bagand thereafter maintaining said clamp means in said closed positionduring movement of said carrier through said region of atmosphericpressure; f) sealing means in said sealing zone for effecting apermanent air-tight seal closure of said clamped bag neck across itsflat width; and g) second activating means after said sealing zone foractivating said drive means to move said clamp means to said openposition thereby releasing said bag neck and allowing the removal ofsaid permanently sealed article-containing bag from said carrier in saidunloading zone.
 16. Vacuum packaging apparatus comprising:a) a pluralityof bag receiving units, each having a support surface for receiving abag to be sealed and a clamp surface for receiving an open neck portionof a said bag; b) transport means for moving said bag receiving unitsthrough a closed path of travel through loading, evacuation, sealing andunloading zones; c) a plurality of vacuum chambers movable through asecond closed path of travel including said evacuation zone, eachchamber being adapted to mate with a bag receiving unit on entry intosaid evacuation zone and to separate from said bag receiving unit onexit from said zone, said chamber and bag receiving unit when matedproviding an air tight seal therebetween; d) evacuating meanscommunicating with each vacuum chamber for evacuating at least part ofthe air from a said bag on said support surface during transit throughsaid evacuation zone; e) a clamp member on each bag receiving unitmovable between an open position spaced from said clamp surface and aclosed position pressed tightly against said clamp surface, said clampmember being arrange to clamp a said open neck portion to substantiallyits flat width; f) drive means on each bag receiving unit operablyconnected to said clamp member and being operable adjacent the exit ofsaid evacuation zone for moving said clamp member to said closedposition prior to said bag receiving unit leaving said evacuation zonethereby clamping shut said open bag neck received on said clamp surfaceand preserving the evacuated state of a said bag upon separation of saidvacuum chamber and bag receiving unit; g) sealing means in said sealingzone engagable against a portion of a said clamped bag neck to effect apermanent air-tight seal of the clamped bag neck across its flat width;and h) said drive means being operable in reverse adjacent the entry ofsaid unloading zone for moving said clamp member to its open positionthereby releasing a said bag neck and allowing the removal of a sealedbag from said support surface.
 17. Vacuum packaging apparatus as inclaim 16 wherein each of said bag receiving units comprises:a) acarriage fixed to said transport means for movement through said closedpath of travel; b) a platen carried by said carriage, said platenincluding said support surface and said clamp surface being disposedtransverse said platen; and c) means mounting said platen to permitrotation to said platen with respect to said carriage in an arc of about90° between a first position wherein said clamp surface is orientedtransverse said carrier path of travel and a second position whereinsaid clamp surface is oriented generally parallel to said carrier pathof travel.
 18. Vacuum packaging apparatus as in claim 17 including meansbetween said evacuating zone and sealing zone for rotating said platenfrom said first position to said second position.
 19. Vacuum packagingapparatus as in claim 18 including means between said sealing zone andsaid loading zone for rotating said platen from said second position tosaid first position.
 20. Vacuum packaging apparatus as in claim 16wherein said sealing means comprises at least one band heat sealer andsaid transport means operates to move said bag receiving unitscontinuously through said sealing zone.
 21. Vacuum packaging apparatusas in claim 16 wherein said sealing means comprises at least one impulseheat sealer and said transport means operates to move said bag receivingunits intermittently through said sealing zone.
 22. Vacuum packagingapparatus as in claim 16 comprising a plurality of actuators positionedat fixed locations along said closed path of travel for triggering theoperation of said drive means including:a) a first actuator at a fixedposition at the entrance to said evacuation zone engageable with saiddrive means and operable to move said clamp member from its openposition to a partly closed position wherein said clamp member holdssaid bag neck to said clamp surface at spaced locations, the areas ofsaid bag neck between said spaced locations being unclamped to permitthe exhaust of air from said bag; b) a second actuator at a fixedposition in said evacuation zone and adjacent the exit thereof operableto cause said drive means to move said clamp member to said closedposition; and c) a third actuator at a fixed position between saidsealing zone and unloading zone and engageable with said drive means formoving said clamp member from said close position to said open position.23. Vacuum packaging apparatus as in claim 16 wherein said drive meansincludes a gear train having a cam follower at an input end and a linkat an output end operably connected to said clamp member, the movementof said cam follower in one direction rotating said gear train tooperate said link and clamp member; and a first actuator at the entranceof said evacuation zone and positioned in the path of travel of said camfollower for rotating said cam follower in said one direction. 24.Vacuum packaging apparatus as in claim 23 having an overcenter lockincluding bias means operating through said gear train to urge saidclamp member to either its open or closed positions.
 25. Vacuumpackaging apparatus as in claim 24 including;a) a slidable stop in thepath of said clamp member for preventing said clamp member from movingto said closed position responsive to the urging of said bias means,said stop and clamp member being engaged at a partly closed positionwherein said clamp member holds said bag neck to said clamp surface atspaced locations; b) a stop release means carried by said vacuum chamberoperable to kick said slidable stop out of engagement with said clampmember thereby allowing movement of said clamp member to its closedposition response to the urging of said bias means; and c) a secondactuator located in the evacuation zone and positioned in the path oftravel of said stop release means for operating a said stop releasemeans as it traverses said second actuator
 26. Vacuum packagingapparatus as in claim 25 including a third actuator positioned betweensaid sealing zone and unloading zone in the path of said cam followerfor rotating said cam follower in a reverse direction thereby rotatingsaid gear train in reverse to move said clamp member to said openposition.
 27. Vacuum packaging apparatus as in claim 16 wherein each ofsaid bag receiving units has a transverse anvil upstanding from saidsupport surface adjacent one end of said bag receiving unit and an uppersurface of said anvil comprises said clamp surface, a said bag receivedon said support surface having its neck portion draped across said anvilupper surface.
 28. A method of vacuum packaging articles in sealablebags comprising the steps of:a) providing a platen movable in a closedpath through successive loading, evacuating and sealing zones; b)placing an open sealable bag containing the article to be packaged onthe platen at the loading zone, drawing the open neck of the bag to aflat width and draping it over a clamp surface such that the bag neck isoriented transverse the platen path of travel; c) moving the platen withthe article-containing bag to an evacuation zone and at least partiallyevacuating air from the bag through the open neck; d) while maintainingat least a partial vacuum in said evacuation zone, clamping the bag neckat its flat width to the clamp surface and thereby effecting a temporaryair-tight seal of the bag; e) moving the platen from the evacuation zoneto the sealing zone and exposing the bag in transit to atmospherepressure while maintaining the temporary air-tight seal thereof; f)rotating the platen with respect to its path of travel for orienting thebag neck in the direction of the platen path of travel prior to enteringthe sealing zone; g) sealing the clamped bag neck across its flat widthin the sealing zone to effect a permanent air-tight seal closure of thebag mouth; and h) moving the platen from the sealing zone to anunloading zone, unclamping the bag neck and removing the sealed bag. 29.Vacuum packaging apparatus comprising:a) a plurality of bag receivingunits; b) transport means for moving said bag receiving units in aclosed path of travel through successive loading, evacuation, sealingand unloading zones; c) each bag receiving unit including(i) a carriagefixed to said transport means, (ii) a platen on said carriage, saidplaten having a support surface for receiving a bag to be sealed and aclamp surface for receiving an open neck portion of a said bag and saidclamp surface being disposed transverse said platen; d) means mountingsaid platen to said carriage to permit the rotation of said platen withrespect to said carriage in an arc of about90° between a first positionwherein said clamp surface is oriented transverse the path of travel ofsaid carriage and a second position wherein said clamp surface isoriented generally parallel to said carriage path of travel; e) aplurality of vacuum chambers movable through a second closed path oftravel including said evacuation zone, each chamber being adapted tomate with a bag receiving unit on entry into said evacuation zone and toseparate from said bag receiving unit on exit from said zone, saidchamber and bag receiving unit when mated providing an air tight sealtherebetween; f) evacuating means communicating with each vacuum chamberfor evacuating at least part of the air from a said bag on said supportsurface during transit through said evacuation zone; g) a clamp memberon each bag receiving unit movable between an open position spaced fromsaid clamp surface and a closed position pressed tightly against saidclamp surface said clamp member being arrange to clamp a said open neckportion substantially its flat width; h) drive means on each bagreceiving unit operable adjacent the exit of said evacuation zone formoving said clamp member to said closed position prior to said bagreceiving unit leaving said evacuation zone thereby clamping shut saidopen bag neck received on said clamp surface and preserving theevacuated state of a said bag upon separation of said vacuum chamber andbag receiving unit; i) sealing means in said sealing zone engagableagainst a portion of a said clamped bag neck to effect a permanentair-tight seal of the clamped bag neck across its flat width thereof;and j) said drive means operable in reverse adjacent the entry of saidunloading zone for moving said clamp member to its open position therebyreleasing a said bag neck and allowing the removal of a sealed bag fromsaid support surface.
 30. Vacuum packaging apparatus comprising:a) aplurality of bag receiving units, each having a support surface forreceiving a bag to be sealed and a clamp surface for receiving an openneck portion of a said bag; b) transport means for moving said bagreceiving units, through a closed path of travel through successiveloading, evacuation, sealing and unloading zones; c) a plurality ofvacuum chambers movable through a second closed path of travel includingsaid evacuation zone, each chamber being adapted to mate with a bag andto separate from said bag receiving unit on exit from said zone, saidchamber and bag receiving unit when mated providing an air tight sealtherebetween; d) evacuating means communicating with each vacuum chamberfor evacuating at least part of the air from a said bag on said supportsurface during transit through said evacuation zone; e) a clamp memberon each bag receiving unit movable between an open position spaced fromsaid clamp surface and a closed position pressed tightly against saidclamp surface said clamp member being arrange to clamp a said open neckportion to substantially its flat width; f) drive means on each bagreceiving unit operably connected to said clamp member; g) a firstactuator at a fixed position at the entrance to said evacuation zoneengagable with said drive means for operating said drive means to movesaid clamp member from its open position to a partly closed positionwherein said clamp member holds said bag neck to said clamp surface atspaced locations, the areas of said bag neck between said spacedlocations being unclamped to permit the exhaust of air from said bag; h)a second actuator at a fixed position in said evacuation zone andadjacent the exit thereof engagable with said drive means for operatingsaid drive means to move said clamp member to said closed position priorto said bag receiving unit leaving said evacuation zone thereby clampingshut said open bag neck received on said clamp surface and preservingthe evacuated state of a said bag upon separation of said vacuum chamberand bag receiving unit; i) sealing means in said sealing zone engagableagainst a portion of a said clamped bag neck to effect a permanentair-tight seal of the clamped bag neck across its flat width thereof;and j) a third actuator at a fixed position between said sealing zoneand unloading zone and engagable with said drive means for operatingsaid drive means to move said clamp member from said closed position tosaid open position adjacent the entry of said unloading zone therebyreleasing a said bag neck and allowing the removal of a sealed bag fromsaid support surface.
 31. Vacuum packaging apparatus comprising:a) aplurality of bag receiving units, each having a support surface forreceiving a bag to be sealed and a clamp surface for receiving an openneck portion of a said bag; b) transport means for moving said bagreceiving units through a closed path of travel through successiveloading, evacuation, sealing and unloading zones; c) a plurality ofvacuum chambers movable through a second closed path of travel includingsaid evacuation zone, each chamber being adapted to mate with a bagreceiving unit on entry into said evacuation zone and to separate fromsaid bag receiving unit on exit from said zone, said chamber and bagreceiving unit when mated providing an air tight seal therebetween; d)evacuating means communicating with each vacuum chamber for evacuatingat least part of the air from a said bag on said support surface duringtransit through said evacuation zone; e) a clamp member on each bagreceiving unit movable between an open position spaced from said clampsurface and a closed position pressed tightly against said clamp surfacesaid clamp member being arrange to clamp a said open neck portion tosubstantially its flat width; f) drive means on each bag receiving unitfor moving said clamp member, said drive means including a gear train, acam follower at an input end of said gear train and a link at an outputend operably connected to said clamp member, the movement of said camfollower in one direction rotating said gear train to operate said linkfor moving said clamp member to said closed position prior to said bagreceiving unit leaving said evacuation zone thereby clamping shut saidopen bag neck received on said clamp surface and preserving theevacuated state of a said bag upon separation of said vacuum chamber andbag receiving unit; g) a first actuator at the entrance of saidevacuation zone and positioned in the path of travel of said camfollower for rotating said cam follower in said one direction; h)sealing means in said sealing zone engagable against a portion of a saidclamped bag neck to effect a permanent air-tight seal of the clamped bagneck across its flat width thereof; and i) said cam follower beingoperable in reverse adjacent the entry of said unloading zone to operatesaid link for moving said clamp member to its open position therebyreleasing a said bag neck and allowing the removal of a sealed bag fromsaid support surface.